textproduct: Rapid City

KEY MESSAGES

- Snow will transition to rain this afternoon and evening. Freezing rain expected across northwest/central South Dakota tonight and Thursday morning.

- Long duration snow expected Friday through Saturday. Moderate accumulations possible.

- Dry and warmer early next week.

DISCUSSION

(Today Through Tuesday) Issued at 320 AM MST Wed Dec 10 2025

Upper air analysis continues to show stubborn northwest flow across the western to central CONUS. Behind the departing compact low over the Midwest, weak ridging is approaching from central/eastern Montana. The next wave is just behind it, crossing the northern Rockies to near central MT. At the surface...high pressure is quickly moving in from eastern MT. Winds will continue to weaken early this morning from west to east. Mostly clear/sunny skies across the majority of the CWA will make for a quiet morning. Highs today will range from near 30 over NW SD to upper 40s over NE WY. The next wave approaches later today. Warm H80-70 flow will increase from the W/SW, providing warm air advection, leading to overrunning. H70 frontogenesis/isentropic lift will support rain (or snow transitioning to rain) through the afternoon and evening. Most areas will warm to above freezing as the warm front works through CWA...but it will fail to reach NW/Central SD. This will lead to a freezing rain event. This icy precip will begin late this afternoon as snow, transition to light freezing rain in the evening, then continue overnight until the precip slides east of the CWA border. Ice accumulation up to a tenth of an inch is expected. There is a second resurgence of precip in the late Thursday morning as a weak cold front pushes into NW SD. Guidance from 00z model runs show CAA lacking with this front, allowing temps to warm above freezing and end the threat of icing. A stronger secondary front will cross the area in the late afternoon/early evening. NBM 25/75 percentiles show max temps at Hettinger ND ranging from 37 to 48...and at Faith 40 to 53 degrees. That is promising for melting of the ice and ending any impacts to travel. Will that in mind, see no need to make changes to the Winter Weather Advisory area and timing. Chances for rain will linger across NE WY and far western SD through the day on Thursday...and a rain/snow mix over the Black Hills. The Thu evening cold front will drop temps back below freezing overnight. As previous shift astutely mentioned...this could result in wet roads icing up overnight in time for the Friday commute as temps drop 30-40 degrees in 18 hours. Overnight snow will linger through Friday over NE WY/NW SD/Black Hills, with good agreement on 1 to 4 inches of accumulation...the highest over the Black Hills. Models show a strong wave crossing ND on Friday, bringing another round of snow to NW/Central SD...and 1 to 4 inches. Models are having difficulty with the placement of overlapping snow totals from both events. Am going middle of the road with totals in the 2 to 6 inch range through a 48 hour period. The beginning of next week could finally bring a pattern change...and with it dry weather and above average temperatures.

AVIATION

(For the 12Z TAFS Through 12Z Thursday Morning) Issued At 320 AM MST Wed Dec 10 2025

VFR conditions will prevail through this morning as high pressure briefly moves in. MVFR/IFR conditions will redevelop over northeastern WY/northwestern SD this afternoon/evening as mixed precipitation develops. MVFR/IFR conditions will spread tonight to NW/Central South Dakota as snow transitions to freezing rain.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Winter Weather Advisory from 5 PM this afternoon to 11 AM MST Thursday for SDZ001-002-012>014-032-078. WY...None.